If money isn't an issue, or you can find a good used one (next to impossible in the current climate though), the HK P2000 with flat base plates is near identical in size to your P239 with 13+1 rds of 9mm instead of 8+1 rds. Both the mag release and slide release are ambi.

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Know the status of your weapon
Keep your muzzle oriented so that no one will be hurt if the firearm discharges
Keep your finger off the trigger until you have an adequate sight picture
Maintain situational awareness